COMMISSION 27 OF THE I.A.U.
INFORMATION BULLETIN ON VARIABLE STARS
Number 2944
Konkoly Observatory
Budapest
9 October 1986
HU ISSN 0374 - 0676
PHOTOMETRIC STUDIES OF THE ECLIPSING VARIABLE V368 Cas
The eclipsing binary star V368 Cas (BD +59d0607, HD 19644) was
photoelectrically observed during 1980 to 1982 in BV and during 1983 in UBVR with
the 0.5-m telescope of Ural University Observatory. The spectral type is B3 III
according to GCVS III. There were obtained 520 photometric measurements in
BV and 80 ones in UR with root mean square errors +-0.016m; +-0.008m; +-0.008m;
+-0.009m for UBVR accordingly. BD +55d0567 was used as comparison star. The
observations were published by Polushina (1984), and yielded four times of
minima, which are given in Table I. Using the above new photoelectric minima
together with the photographic minimum given by Strohmeier (1959), the new
ephemeris has been derived as follows:
JD I min = 244 5435.3089 + 4.4516321d E.
The observations are illustrated in Figure 1.
Table I
V368 Cas times of minima
JD(hel) filter min (O-C)_GCVS
244 5000+
326.2437 B,V II -0d0442
386.3409 B,V I -0.0442
386.3407 U,R I -0.0444
435.3089 U,B,V,R I -0.0443
Each light curve has been considered as an independent source of
information. The Russell-Merill method was used for calculation. Least-squares
solutions were made for the light at the maxima according to the formula
1=A_0 + A_1CosTheta + A_2Cos2Theta.
Fourier coefficients as well as the number of points outside the eclipse
are given in Table II. The solution was obtained in a completely automatized
manner with Lavrov's computer program (1982) for "Nairi-K" computer. Because
of the small number of U, R observations minima, B, V light curves were
used for calculate the photometric elements. The main variable parameters
for the solution are the orbital inclination angle i, the unperturbed
relative radius of the less component r_2, the ratio of the unperturbed radii
k=r_2/r_1. A circular orbit has been adopted. Photometric elements together
with corresponding errors are listed in Table III. According to value p
eclipse in the system is partial. The theoretical light curve in V is
illustrated in Figure 1 with the aid of a solid line. The agreement between the
theoretical light curve and observations seems to be very good. There is,
however, a discrepancy with orbital elements published by Cristescu et al.
(1984).
Table II
Fourier coefficients for the light curves
at the maxima
U B V R
A_0 0.9505 0.9629 0.9566 0.9358
+-48 +-5 +-5 +-32
A_1 -0.0476 -0.0515 -0.0550 -0.0613
+-53 +-7 +-6 +-35
A_2 -0.0077 -0.0120 -0.0134 -0.0188
+-62 +-9 +-7 +-41
n 36 364 364 36
Table III
Photometric elements of V368 Cas
V B V B
i 77.9d 78.8d a_2 0.262 0.247
+-1.0 +-1.0 +-30 +-44
k 0.924 0.873 b_2 0.254 0.241
+-75 +-55
a_1 0.283 0.283 L_1 0.816 0.864
+-25 +-15
b_1 0.275 0.276 x_1 0.35 0.17
+-.27 +-.26
c_1 0.269 0.271 x_1 0.53 0.27
+-.30 +-.44
p -0.317 -0.302
The spectral type A1 for the cooler component follows from the ratio
of surface brightnesses. Effective temperatures by Popper (1980) were used.
The star is greater in size for its spectral type, i.e. it is obvious that
it has already evolved. In fact V368 Cas evolved through mass exchange.
[FIGURE 1]
Figure 1. Light curves of V 368 Cas
Assuming an A-star filling its Roche-lobe, it was possible to estimate the
absolute parameters of the orbit. We have obtained these for mass ratio
q=0.24, using the empirical spectral type-mass and mass-radius relations for
main sequence stars by Svechnikov et al. (1984 a,b);
R_B = 6.4R_sun; M_B = 6.7M_sun
R_A = 5.7R_sun; M_A = 1.7M_sun
A = 23.04R_sun
Acknowledgements. Thanks are due to Dr. M.I. Lavrov for the aid in
the practical use of his program, and to M. A. Svechnikov for useful
suggestions and constructive comments.
T.S. POLUSHINA
Urals University Observatory
Sverdlovsk, U.S.S.R. 620083
References:
Cristescu C., Oprescu G., Suran M.D. 1984, IBVS 2517.
Lavrov M.I. 1982, "Mashinnyj analiz krivjkh bleska zatmennykh dvojnykh zvezd.
II. Prjamoj metod i ego programmirovanie dlja EVM "Nairri-K" Kazanskj un.,
Kazan' 1981. Dep. v VINITI N 797-82.
Polushina T.S. 1984, "Metody astronomo-geodezicheskikh issledovanij",
151. Sverdlovsk. [BIBCODE 1984magi.conf..151P ]
Popper D.M. 1980, Ann. Rev. Astron. and Astrophys. Vol. 18. 115. [BIBCODE 1980ARA&A..18..115P ]
Strohmeier W. 1959, Veroff. Rem.-S. Bamberg 5, N3.
Svechnikov M.A., Tajdakova T.A. 1984a, Astron. Zh. Sov. 61, 1, 143. [BIBCODE 1984AZh....61..143S ]
Svechnikov M.A., Bessonova L.A., Dubinina N.A., 1984b, "Nauchnye informacii
Astron. Sov. AN USSR" N50, 56. [BIBCODE 1982NInfo..50...56S ]